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Mongoose

Mongoose Legion Kids Freestyle Sidewalk BMX Bike

  • Based on 4,148 reviews
Condition: New
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Availability: In Stock.
Fulfilled by Amazon
Arrives Sep 19 – Oct 2
Order within 23 hours and 31 minutes
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Size: 18-Inch Wheels/L18


Color: White


Features

  • SCALED FOR YOUNG SHREDDERS: Designed for riders 3'8" to 4'2" tall, this kid-sized BMX bike pairs 18-inch wheels with scaled-down components to deliver a true BMX experience in a bike that fits young riders just right.
  • CONFIDENT GRIP: Wide 2.3-inch tires provide confident traction on pavement, park surfaces, and packed dirt. Built to help riders stay planted while building skills and trying something new.
  • BUILT FOR PROGRESSION: A durable 1-piece crank helps keep pedaling smooth and reliable while developing strength, balance, and bike control through every stage of learning.
  • READY FOR EVERY SESSION: A durable steel rear hub is designed to handle everyday riding, while the alloy U-brake delivers dependable stopping power for practicing first tricks and dialing in control.
  • KNOW YOUR ROOTS: As one of the OGs in action sports, Mongoose has helped bring the BMX movement to the world. For over 50 years, we've been all about epic rides and pushing limits and we're just getting started.

Description

For 45 years, Mongoose has been in the dirt, down the trails, and on the ramps. With the Legion Series, Mongoose offers a full line of freestyle BMX bikes for riders of all ages and ability levels. The Legion L20 was designed to be a fully park, street and dirt worthy BMX bike. The Legion L20 features a Hi-Ten steel frame (20.25” top tube), tapered headtube, and removable brake mounts. The L20 Hi-Ten steel 8” rise handlebar and 48mm stem are designed for precision riding, while the wide aluminum single wall 36H rims and 2.3” BMX tires offer grip and durability. The 25x9T gearing with one-piece tubular chromoly 170mm hollow spindle cranks and American loose ball bottom bracket offer a clean, reliable drivetrains. An alloy U-brake with alloy brake levers provide speed control, while the Hi-Ten Steel BMX fork with 1-1/8" threadless steerer and taper leg helps maximize performance. This bike ships ready to be assembled and comes with a 5-year limited warranty on the frame and a 1-year limited warranty on parts.

Bike Type: BMX Bike, Kids Bike


Age Range (Description): Little Kid


Brand: Mongoose


Number of Speeds: 1


Color: White


Wheel Size: 18 inches


Frame Material: High Tensile Steel


Suspension Type: Rigid


Special Feature: Adjustable Seat


Included Components: Reflectors, User Manual


Bike Type: BMX Bike, Kids Bike


Number Of Speeds: 1


Suspension Type: Rigid


Additional Features: Adjustable Seat


Brake Style: U Brake


Specific Uses For Product: Freestyle


Power Source: Manual


Intended Riding Terrain: BMX Terrain, Paved Roads, Urban Terrain


Bicycle Drivetrain Type: Chain Drive


Color: White


Wheel Size: 18 inches


Size: 18-Inch Wheels/L18


Wheel Width: 2.35 inches


Item Weight: 23.2 pounds


Warranty Type: Limited


Maximum Weight Recommendation: 100 pounds


Minimum User Height: 44 inches


Age Range Description: Little Kid


Brand Name: Mongoose


Included Components: Reflectors, User Manual


Model Number: M4126G27U1OS11


Model Name: Legion L18


Model Year: 2026


UPC: 038675293700


Manufacturer: Mongoose


Unit Count: 1 Count


Item Type Name: BMX Bicycle


Warranty Description: Limited lifetime warranty on frame. 1 year limited warranty on parts. 30 day limited warranty on wearable parts.


Frame Material Type: High Tensile Steel


Wheel Material: Aluminum


Seat Material: Polyvinyl Chloride (PVC)


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Sep 19 – Oct 2

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Similar Products

Top Amazon Reviews

    • Extremely Easy to Assemble. Bike Looks Amazing. M8x1.25 Tap May be Needed.
Size: 20-Inch Wheels/MAG Color: Orange
Review Image by Dave
Review Image by Dave
Review Image by Dave
Review Image by Dave
Review Image by Dave
Review Image by Dave
The bike from the pictures looked pretty cool. I didn't realize how beautiful this bike would be until it came in the mail. I purchased the Legion Mag in orange for my 8 year old. It was great to see his reaction on Christmas when receiving this bike. He was so excited. I read some other reviews from reviewers who had complaints on the difficulty of assembling the bike and in my opinion the people having trouble assembling the bike must be blatantly ignorant or illiterate. The instructions for assembly are written so a teenager could assemble this bike, with clearly labeled diagrams and more in depth explanations than what is necessary for assembly. The instructions on assembly are excellent and I had almost no trouble assembling the bike without them until it came to adjusting the brakes. I assembled the entire bike without instructions except for the brakes because it is just self explanatory. I was also able to assemble the brakes without any trouble or needing the instructions although I did refer to them for proper adjustment and alignment protocols. The only issue I had when assembling the bike is when I got to the point of attaching the handlebars to the handlebar binder assembly attached to the stem. The four socket cap screws that tighten down on the handlebar binder bracket would not thread easily. I felt as though I would break the screws or destroy the threads if I attempted to tighten them down far enough to grip the handlebars. There was too much paint in the threaded holes and also the tolerances on the machining of the threads was not great. I have included some pictures showing just how much paint was removed from tapping and also chips from burs in the threaded holes from poor tolerance drilling and tapping at the factory. In order to fix this problem I grabbed a tap handle and a M8x1.25 normal thread tap and tapped the holes. I would give this bike a 4.9 out of 5 if I could just because I needed to tap these holes and a tap was not listed as a required tool. I don't think many people will have problems assembling the bike even if they have this issue and need to tap the four holes as these are the only holes that need anything to be screwed into. Honestly if you don't at the very least know how to use a tap and die set you probably shouldn't be assembling a bike as it's not safe to do so if you're not familiar with basic tools. You could wind up hurting your child from pure negligence if you don't know how to use basic hand tools to assemble this bike properly. My suggestion is that you take it to a local bike shop and pay $30-$40 to have them assemble the bike and adjust the brakes if you don't know what you are doing. I assume some people who buy this bike will do just that with the majority of people knowing how basic hand tools work and them being able to assemble it themselves. Overall the bike is amazing, my son loves it, it was extremely easy to assemble, and I recommend you tap the holes on the handlebar binder even if it doesn't need it as it will allow you to make a more secure connection. Please don't listen to people complaining about difficult assembly as it was extremely easy even the detangler brakes something of which I've never seen or dealt with on a bike before. The instructions are very clear on how to hook the brakes up and how to adjust them properly and I was actually surprised how easy it was to assemble the brakes because I was expecting something very difficult based on the reviews but it turns out these brakes are easier to assemble than normal brakes. ... show more
Reviewed in the United States on December 30, 2020 by Dave
    • Great bike
Size: 18-Inch Wheels/L18 Color: Silver/L18
My son, absolutely loved this bike when he received it, and it was put together, the bike was perfect for his size. It rode very smooth and I feel like I got what I paid for unfortunately after moving into our new place, the bike was stolen from our backyard
Reviewed in the United States on May 29, 2026 by Latisha
    • Good quality Bike
Size: 20-Inch Wheels/MAG Color: Orange
Great Bike for a beginner and a leap above Huffy and Walmart bikes. I remember Mongoose being a Good recognizable brand decades ago. This bike was easy to assemble. I think it took an hour to unbox and put together. Box was damaged heavily, but bike was packed so well with foam and wrapping that there wasn't a single scratch. The most important part is the kid is happily surprised and liked the color. ... show more
Reviewed in the United States on March 2, 2026 by The Real Hughleys
    • What brakes?
Love the bike. Bought 2 of them for my kids for Christmas. Put them together. it wasn't hard but i've been building bikes for like 20 years. my only gripe with these bikes is the brakes... or should i say, lack there of brakes. the brake pads just dont work worth a darn. i'm going to buy new pads to replace these garbage ones. overall, the kids love the bikes. they love the rims, but say they cant stop quick enough... i can pull both breaks super tight and still push the bike and the wheels turn... like, seriously bad breaks. ... show more
Reviewed in the United States on January 20, 2024 by Amazon Customer
    • Great people
Size: 20-Inch Wheels/MAG Color: Orange
Great bike. And during shipping the chain Guard got broken, Pacific Cycle was awesome replacing it quick and friendly. A great shopping experience. Thanks guys
Reviewed in the United States on January 21, 2026 by James Cutsforth
    • A very happy kid!!
Size: 20-Inch Wheels/MAG Color: Orange
Mya nephew was very happy......
Reviewed in the United States on May 3, 2026 by Imanuel Hodges
    • I Will NEVER buy another Mongoose
Size: 20-Inch Wheels/MAG Color: Orange
With all of the four and five star ratings, I must be the problem, right? The bike came partially dissembled for shipping purposes. I expected that. What I did not expect was: 1. Missing parts. One of the nuts and both of the washers were missing from the front wheel. Ok. A shipping problem. But what kind of washers do I need to go find? Should be simple. Just read the instructions. 2. Horrible Instructions: For example, to attach the front wheel, I need to follow the appropriate set of instructions depending if my bike's wheel is, "nutted with step retaining washer, nutted with clip retaining washer or quick release". But I don't know which one my bike is; the nut and both washers are missing. Every section is just like this; follow the set of instructions that pertain to your bike. But where does it say if the bike I purchased has a quill stem, a threadless stem, a front load stem or a top load stem? I have no idea. Mongoose has been around for a while. So there are plenty of videos on YouTube. But there are so many configurations for Mongoose bikes, good luck finding the right one. I watched a bunch of videos, went to Wal-Mart (twice) and got $30 worth of nuts, washers, hex drivers and, no I didn't go out and buy the lithium gel they recommended! Then I paid a bike shop $45 to put the thing together because I still couldn't figure it out. The bike shop wouldn't do the brakes because of liability purposes. But they showed me that I needed to loosen a nut and put the brake cable out some. Should be easy, except... 3. CHEAP parts!: I stripped a nut and two screws trying to tighten the brakes just enough to barely work. It's Christmas Eve and I'm soooo frustrated. Should I be worried? Every single step in the instruction book says that if I don't do this step correctly, someone could get seriously injured or killed. Here ya' go son. Have fun! Merry Christmas. I could call Mongoose Customer Support. They are open Monday through Friday 8 to 5; because that's when dads assemble bikes right? Sorry for all of the venting. I've had the bike for a week and I have to say, I have NEVER had this much trouble assembling something that came in a box. I've got $250 invested into a $170 bike and I don't feel safe letting my son ride it. I am not a happy customer. ... show more
Reviewed in the United States on December 25, 2020 by Jared D.
    • Go B Go
Size: 18-Inch Wheels/L18 Color: Silver/L18
Easy to put together, perfect fit for 6 year old, color and look were outstanding. Brakes were only on Front wheel which surprised me but worked perfectly.
Reviewed in the United States on January 11, 2025 by HorsemanWili

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